1. Field of the Invention
The present invention relates to piston with a basic piston barrel of forged steel and a cooling channel. In particular, this invention relates to a piston in which deformation in the region of the ring band is minimized.
2. The Prior Art
This type of a piston and a process for its manufacture are known from German Patent No. 44 46 726 Al. However, the piston shown in this patent has the drawback that the ring band is tied to the basic piston barrel only via the piston head. Thus, the ring band is consequently susceptible to deformation.
A piston made of cast iron is known from PCT Application WO 80/02308, where the top part and the boss part are welded together. This piston has a rib extending all around above the bosses; however, this rib is not welded to the top part and has no stiffening function.
Another piston of this type is shown in German Patent No. DE 24 34 902 A, where sections of the ring band and a radially outward section of the piston head are formed by a welded-in component. This measure, however, exclusively forms a cooling channel. This is a problem which has been solved already in the relevant state of the art by closing the machined cooling channel with a metal sheet.
Another piston is shown in German Patent No. DE 30 32 671 A, where a top part made of heat-resistant steel and a bottom part made of flow-pressed steel are welded together.